Inhibited antifreeze composition



United States Patent 7 Claims. 01252-45 ABSTRACT OF THE DISCLOSURE A corrosion inhibited alcohol/water antifreeze contains mercaptothiazoline together with an alkali metal salt of tetraboric acid and alkali metal carbonate or hydroxide in the molecular ratio of 1:2-4. The composition also contains an alkali metal silicate.

This invent-ion relates to an inhibited antifreeze composition which is particularly suitable for addition to the cooling water in motor car radiators.

Radiators of motor vehicles must be filled in winter with liquids which are not subject to the formation of ice crystals at temperatures below 0 C. Various alcohols may be mixed with the radiator water for this purpose but the most commonly used are glycerol and, particularly, ethylene glycol. A variety of materials are also incorporated for the purpose of reducing corrosive tendencies of the final composition. These additives are often mixed with the antifreeze component and the resulting mixture is usually known as an inhibited antifreeze.

In order to obtain and advantageous power/weight relationship it is becoming common to use light metals as well as iron and non-ferrous metals in the construction of engines. -In addition the engines are being operated under more and more rigorous conditions (e.g. high compression, high r.p.m. and the use of super-chargers) with the result that the operating temperature of the engine increases so that the radiator liquid has to carry away more heat. This naturally produces higher water temperatures and therefore the corrosive tendency increases.

In spite of the more stringent operating conditions it is becoming common to leave the antifreeze in the radiator for two years during both summer and winter so that servicing is reduced to topping up to replace the water which has evaporated. Thus there is an even greater need to reduce the corrosive tendencies of the radiator fluid.

As has been indicated above the radiator system of an engine often contains a variety of different metals and it is clearly important that there shall be a low corrosive tendency in respect of all the metals present in the radiator system. It is important to realise that low corrosion rates may be even more important in the case of metals which form only a small proportion of the radiator system than in the case of metals which form the bulk of the construction. Thus, for example, solder, aluminium and bearing metals have to perform an important function and relatively small amounts of corrosion on these materials may be of greater significance than much greater corrosion in respect of the main metal of construction, e.g. cast iron or steel. Thus it is an object of the present invention to reduce the corrosive tendency of antifreezes in respect of many metals which are likely to be found in a radiator system.

According to the invention an inhibited antifreeze, suitable for use in water-based radiator liquids, consists of:

(a) a water-miscible alcohol, preferably ethylene glycol,

3,362,910 Patented Jan. 9, 1968 ICC (b) an alkali metal silicate, preferably sodium metasilicate,

(c) mercaptothiazoline and/or mercaptobenzothiazole,

(d) an alkali metal salt of tetraboric acid, preferably sodium tetraborate, and

(e) an alkaline reacting compound of an alkali metal,

preferably sodium carbonate, sodium hydroxide, potassium carbonate or potassium hydroxide,

(f) at least sufiicient water to maintain the other components in solution,

the molecular ratio of component (d) to component (e) being 122-4.

When component (e) is sodium carbonate the preferred molecular ratio is 1:3-3.5 and when component (2) is sodium hydroxide the preferred molecular ratio is 122.0- 3.0. In addition to the ingredients just specified benzarnide and/or phthalimide may be incorporated as additional ingredients.

A particularly suitable inhibited antifreeze composition according to the invention consists of:

Percent by weight Sodium metasilicate 0.005-0.25 Mercaptothiazoline and/or mercaptobenzothiazole 0.005-0.25

Sodium tetraborate 0.262.6 Sodium carbonate 0.28-5.6 Benzamide and/0r phthalimide 0-0.5 Water 1.5-30

Ethylene glycol to make Percent by weight Sodium metasilicate 0005-025 Mercaptothiazoline and/or mercaptobenzothiazole 0.005-0.25 Borax 0.5-5.0 Sodium carbonate 0.28-5.6 Benzamide and/or phthalimide 0-0.5 Water 1.2-28 Ethylene glycol to make 100% The same molecular ratio of borax to sodium carbonate applies as in the previous case since there is one molecule of anhydrous sodium bonate contained in .one molecule of borax. In both cases the quantity of water should be sutficient to maintain the components in solution; in effect this means that the quantity of water is controlled by the quantity of sodium carbonate.

Six compositions according to the invention will now be described by Way of example; these are identified as compositions I-VI. These compositions according to the invention will be compared with four other compositions illustrating borate-carbonate ratios outside the range of our invention; these comparative compositions are hereinafter identified as Cl-4. The specification also includes information on prior art compositions and these are designated as P1-9.

The formulation of the compositions according to the invention and also of comparative compositions C1-4 are given in Table 1. In this table the figures represent the percent by weight of the various components and the figures in the row labelled Ratio gives the number of 4 (in accordance with British specification DTD 779).

Composition P7: Percent by weight mollewiar p p t g g g gg for each Ethylene glycol 975 H1O ecu 211' PIOPOI' 10D S 11111). e ra OI BoraX 25 TABLE 1 Invention Higher and Lower Ratios Composition I II III IV I V I VI C1 C2 C3 C4 Sodium liletasilieate c. 0. 05 0.05 0.05 0.05 0 05 0.05 0.05 0.05 0.05 O. 05 Mercaptothiazoliuo 0. 05 O. 05 0. O5 0. 05 0. 05 l\lercaptohenzothiazo1e t 0. 05 0. 05 0. 05 0. 05 0. 05 Sodium Tetraborate... v. .7 0. 40 0.40 0. 4O 0. 40 0. 40 0. 40 1 58 0.26 1.58 0. 26 Sodium Carbonate 0.71 0.71 0.71 0.71 0.71 0.71 0.11 0.10 0.11 I. Benzoamide 0.25 N 1. 0.05 Phthalimide 0. 25 c 0. 05 Ethylene Glycol 95. 14 94. 89 94. 87 95. 14 95. 09 95. 09 96. 29 93. 30 96. 29 931 30 Water v H 3. 65 3. 65 3. 65 3. 65 3. 65 3. 65 1. 92 5. 24 1. 92 5. 24 Ratio 3. 4 3. 4 3. 4 3. 4 3. 4 3. 4 0. 13 7. 9 O. 13 7- 9 Table 2 gives the formulation of the comparative conpositions designated Pl-PS. As in Table l the figures give (in accordance with U.S. specification OE 771a).

Composition P8: Percent by weight Eth lene 1 col 95.0 the percent by weight of the ingredient and the ratio 25 a bgegzoate gives the number of molecular proportions of sodium composition P9: Percent by Weight carbonate to each molecular proportion of borate reck- Ethylene glycol 945 oned as the total of boric acid plus sodium tetraborate Sodium benzoatg 50 plus sodiummetaborate. 30 Sodium nitrite 05 TABLE 2 Composition P1 P2 P3 P4 P5 Sodium Metasilicate. 0v Meroaptobenzothiazol 0. 12 0. 225 Sodium Nitrate 0. 18 0.325 Sodium Nitrite. 0. 5 Boric Acid 0. Sodium Tetraboiate Organic Acids.

Ethylene Glycol- 97. 76 Ratio 0. 39 1.9

The organic acids in Composition P5 were weak unsat- 45 urated acids (or their alkali metal salts) having a molecular weight of 300-350.

The remaining compositions had the following formulations:

For use the compositions described above are normally diluted with l-2 parts by volume of water according to the lowest temperature expected. Tests were carried out on the corrosiveness of the various compositions to a variety of different metals and in these tests the compositions were diluted with two parts by volume of Water (i.e., the test solution consisted of one-third composition Triethanolamine phosphate 1.0 and two-th1rds water). The test results are given in Sodium mercaptobenzothiazole 0.3 Table 3.

TABLE 3.CORROSION TEST ASTM 1384/61 '1 Test Metal Composition GCI A1 S0 Cu BS St +0. 12 +0. 07 +0. 04 +0. 05 +0.07 +0. 20 +0.02 +0. 00 +0. 08 +0.07 +0.25 +0. 04 +0, 07 +0. 08 +0. 09 -0.18 +0. 12 -0. 07 +0. 11 -0. 0. 25 +0. 09 0. 07 -0. 11 -0. 2s -0. 0. 10 +0. 07 0. 11 -0. 30 -1. 96 -0. 51 +0. 04 0. 10 -0. 22 +0.22 -15. 51 -1. -0. 10 -0. a5 -2. 26 --o. 52 +0. 07 -0. 11 -0. 49 -0. 24 -1.15 -0. 07 -0.14 -0. 33 +1. 6 +0.52 +0. 17 +0.08 +0. 10 +0. 52 +0. 21 +0.08 +2. 0 +0 +0. 17 +0.08 +0. 5 +0. 25 +0. 08 +0 +0.27 +0.70 +0.08 +0.08 +0.02 +0. +0.01 +0.02 +0. 21 +0. 3 +2. 18 +0. 11 +0. 04 +0. 17 +0.7 +2. 08 +0.50 +0. 18 +1. 45 +0. 3 +0. 4 +0. 30 +0.20 +0. 10 +0. 30

Figures indicate weight change in rug/cm. Indicates gain. Indicates loss.

The column headings have the following significance:

GCI indicates grey cast iron Al indicates aluminum So indicates a tin/ lead solder Cu indicates copper Bs indicates brass St indicates steel A quick inspection of Table 3 shows that only the compositions according to the invention (IVI) and compositions P4, P5 and P9 have all their results less than 1.0 and therefore only these compositions will be given consideration.

The solder in the radiator system is used for making joints and a relatively small amount of corrosion of the solder may cause a leak. Thus the results in the solder column are of particular significance and it will be noted that compositions P4, P5 and P9 give results of +0.26, +0.70 and +0.30 respectively. The worst result of the compositions according to the invention was given by composition IV with a figure of 0.12. Thus there is a clear advantage in favour of our invention. Of the prior art compositions just mentioned P4 gave the best solder result but it had an aluminum result of +0.5. This figure also compares unfavourably with the worst aluminum figure according to our invention, namely 0.35. This further illustrates the superiority of the compositions according to our invention in reducing the tendency to corrosion in respect of all the metals used in the test.

Thus all the compositions according to our invention display an improvement over the comparative compositions illustrated above. It is however, interesting to note that compositions I, II and III (which contain mercaptothiazoline) gave even better results than those given by Compositions IV, V and VI (which contain mercaptobenzothiazole).

Component ((2) will tend to form salts with the cation present in the antifreez solution. If desired component (c) may 'be added in the form of a salt, e.g. the sodium salt.

We claim:

1. An inhibited antifreeze composition, suitable for use in water-based radiator liquids, and consisting essentially of the following ingredients:

Percent by weight (1) An alkali metal silicate 0.0050.25 (2) A mercaptan selected from group consisting mercaptothiazoline, mercaptobenzothiazole and mixtures thereof 0005-025 (3) Sodium tetraborate 0.265.0

Percent by weight (4) An alkali metal compound selected from the group consisting of sodium carbonate, sodium hydroxide, potassium carbonate and potassium hydroxide 0.28-5.6 Water 1.5-30 A water-miscible alcohol selected from the group of ethylene glycol and glycerol, q.s. to make 100%.

The molecular ratio of the sodium tetraborate to the alkali metal compound being 132-4.

2. A composition in accordance with claim 1 which further includes up to 0.5 by weight of a compound selected from the group consisting of benzamide, phthalimide and mixtures thereof.

3. An antifreeze according to claim 1, in which the alcohol is ethylene glycol.

4. An antifreeze according to claim 1 in which the silicate is sodium metasilicate.

5. An antifreeze according to claim 1, in which the alkali metal compound is sodium carbonate and the molecular ratio of component (d) to component (e) is 1:33.5.

6. An antifreeze according to claim 1, which the alkali metal compound is sodium hydroxide and the molecular ratio of component ((1) to component (e) is 1:20-30.

7. An inhibited antifreeze, suitable for use in Waterbased radiator liquids, which consists of:

Ethylene glycol to make 100%.

the molecular ratio of sodium tetraborate to sodium carbonate being 1:3-3.5 and the quantity of water being at least sufiicient to maintain the other components in solution.

References Cited UNITED STATES PATENTS 1/1962 Truitt 252 2/1964 Morehouse et a1. 25275 LEON D. ROSDOL, Primary Examiner.

S. D. SCHWARTZ, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,362,910 January 9, 1968 Hermann Emil Ferdinand Ordelt et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Columns 3 and 4, TABLE 2, second column, line 4 thereof,

for "9.25" read 3.25 column 5, lines 12 and 13, for "given consideration" read given further consideration line 34, for "gave" read give lines 47 and 48, for "consisting" read consisting of column 6, line 7, for "group of" read group consisting of line 24, for "claim 1, which" read claim 1, in which same column 6, after line 28, as a right-hand heading insert Percent by weight Signed and sealed this 1st day of April 1969.

fiEAL) Attest:

EEHWARD L BRENNER.

Edward M. Fletcher, Ir.

Commissioner of Patents Attesting Officer 

